<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    .card {
      width: 300px;
      height: 200px;
      padding: 20px;
      background-color: #fff;
      box-shadow: 0 0 10px rgba(0,0,0,.2);
      position: relative;
    }
    
    /* 🔥🔥核心: 通过给 card 设置一个 “::before” 从而实现卡片的镂空效果... */
    .card::before {
      content: '';
      position: absolute;
      top: -15px;
      left: -15px;
      bottom: -15px;
      right: -15px;
      z-index: -1;
      border: 2px solid #f00;
      /* ✨元素 - 二维平面倾斜效果实现: */
      transform: skew(-10deg);
    }
  </style>
</head>
<body>
  <div class="card">
    <h3>Card Title</h3>
    <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.</p>
  </div>
</body>
</html>